Cooling system for a liquid-cooled internal combustion engine

ABSTRACT

For a cooling system of a liquid-cooled internal-combustion engine, a charging, venting and pressure control arrangement is suggested. In this case, a compressive stress mechanically generated in the coolant is combined with a forward-flow system control, in which case the gradual shutting-off or reduction of pressure is achieved into a pressureless coolant reserve acted upon by atmosphere. During cold charging, the arrangement provides a rapid filling of the cooling system with the coolant. Checking of the filling level in the reserve chamber in the case of operationally warm coolant without a loss of pressure and the risk of a coolant ejection is also permitted.

This application is a 371 of PCT/EP97/01318 filed Mar. 15, 1997. Thepresent invention is related to the subject matter of European PatentDocument EP-A-0295445.

BACKGROUND AND SUMMARY OF THE INVENTION

In this known cooling system, a tank penetrated by a forward flow pipeis used for separating the air and fuel gas from the coolant. By meansof a relief valve in a valve unit, which is arranged in an elasticallysupported manner against a closure of a filler neck of the tank, theseparated gasses are fed to a compensation, storage and air blockingtank which is acted upon atmospherically. In addition to a coolantreserve, this compensation tank contains an expansion volume whichconsists of a gas cushion under a defined excess pressure.

With respect to compensation tanks which are formed essentially of rigidwalls, for compensation of thermally caused coolant volume changes,elastic connection hoses between the internal-combustion engine and theradiator can be used as additional compensating devices. This is knownper se, for example, from U.S. Pat. No. 3,208,438.

Compensation tanks with devices which are elastically flexible at leastin certain areas are known from U.S. Pat. No. 3,238,932 and GermanPatent Document DD-PS 136280.

In each of the systems described in these documents, the necessarypressure buildup in a respective cooling system takes place bycompressing a buffer air/gas volume, preferably in the compensationtank. A disadvantage, in this case, is that a relatively large expansionvolume is needed in order to be able to absorb the volume increase ofthe coolant under extreme temperature conditions, such as, for example,reheating of a hot-parked internal-combustion engine, in order toprevent a possible coolant ejection or loss. Further, since the pressurebuildup is significantly determined by the volume distribution betweenthe coolant reserve and the buffer gas/air volume in the compensationtank, and when taking into account leakage and evaporation losses, aminimum charging level in the compensation tank is required. Therequirement for a large buffer air/gas volume and a sufficient minimumreserve of coolant results in a relatively large compensation tankwhich, because of its space requirement, is difficult to place in theengine compartment and may cause unfavorable pipe arrangements.

One object of the present invention is to improve a cooling system ofthe above-mentioned type such that the pressure required in the coolingsystem for avoiding both premature boiling and pump cavitation isachieved without a prestressed buffer air/gas volume.

This object is achieved by the present invention, which provides theadvantage of a combination of compressive stress mechanically generatedin the coolant with a forward flow system pressure control. In thiscase, the gradual shutting-off or release of pressure is achieved into a"pressureless" coolant reserve acted upon by atmosphere. This results inan advantageously small charging, venting and pressure controlarrangement which is preferably arranged in the coolant system forwardflow from the internal-combustion engine to the radiator.

Advantageous further features of the invention are also described. Thedetachable arrangement of the valve unit is formed by the relief andvent and return flow valve. Forming the detachable arrangement in thevalve connection piece of the forward flow pipe permits a rapid coldcharging of the whole cooling system with rapid and reliable venting.The arrangement of the valve unit in the valve connection piece by meansof an elastic support against an insert detachably arranged in thefiller neck, in conjunction with the pressureless coolant reserve in anoperationally warm cooling system, makes opening of the reserve chamberpossible without a loss of pressure in the cooling system. Checking ofthe cooling reserve and optionally of the warm charging is permittedwithout any risk for the checking person as a result of coolantejection.

A vent and return flow valve, which connects the compensation chamberwith the reserve chamber, and a vent and return flow valve, whichconnects the forward flow pipe of the cooling system with the reservechamber, are designed as thermostatic valves. Starting from a definedoperating temperature, these thermostatic valves prevent a gas andcoolant exchange and thus advantageously contribute to safe opening ofthe coolant reserve chamber.

The insert described above is detachably arranged in the filler neck andas an abutment for a spring which holds the valve unit in a closedposition with respect to the relief valve. The insert is preferablyconstructed in a pot-shape with a control opening arranged in the bottomfor checking the warm charge level. Finally, the displaceable boundaryof the compensation chamber is a displacement piston which is arrangedby way of roller bellows in a coolant-tight manner and is acted upon bya prestressed pressure spring. The prestressing of the pressure springmay be selected such that, until a predetermined level for reaching thepressure generated by the thermally caused volume change of the coolantin the coolant system is reached, a correspondingly slight displacementof the displacement piston will take place.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention illustrated in the drawings willnow be described.

FIG. 1 is a view of a cooling system for a liquid-cooledinternal-combustion engine;

FIG. 2 is a view of a charging, venting and pressure controlarrangement;

FIG. 3 is a view of the arrangement according to FIG. 2 prepared forcold charging;

FIG. 4 is a view of the arrangement according to FIG. 2 during engineoperation;

FIG. 5 is a view of the arrangement according to FIG. 2 in the case ofwarm charging occurring, for example, while the engine is running; and

FIG. 6 is a view of the arrangement according to FIG. 2 during a coolingoperation of a parked internal-combustion engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A cooling system 1 for a liquid-cooled internal-combustion engine 2comprises a forward flow 3 to a radiator 4 and, from this radiator 4back to the internal-combustion engine 2, a return flow 5 which isconnected to a housing 6 of a thermostat 7. From the housing 6 with thethermostat 7, which, as the result of the operation, closes the shortcircuit 6, the coolant flows by way of a suction pipe 9 to a pump 10which conveys the coolant into the internal-combustion engine 2.

A charging, venting and pressure control arrangement 11 according to theinvention is arranged in the forward flow 3 between theinternal-combustion engine 2 and the radiator 4.

According to FIGS. 2 and 6, the arrangement 11 comprises a tank 12 whichis penetrated by a forward-flow pipe 13 connected with the forward flow3. The forward flow pipe 13 has a fixedly arranged valve connectionpiece 14 which is arranged to sealingly penetrate a partition 15 of thetank 12 and by means of its valve opening 16 leads into a chamber 17 fora coolant reserve 18 which is acted upon by atmosphere.

Below the partition 15, the tank 12 has another geodetically deeperchamber 19 which, by means of a displacement piston 21, which can bedisplaced against the elastic resistance of a pressure spring 20, isused for coolant volume compensation. The displacement piston isassigned in a coolant-tight manner to the compensation chamber 19 by theroller bellows 22.

By way of a connection piece 23 and a pipe 23', this compensationchamber 19 is in a coolant-carrying connection with the pump suctionpipe 9 illustrated in FIG. 1. The compensation chamber 19 is connectedwith the coolant-reserve chamber 17 by way of a temperature-controlledventing and return flow valve 24. It is known that thermostats of thistype are equipped, for example,. with a bimetallic element which, aftera defined temperature is exceeded, brings a ball valve into the closingposition and holds it there.

In the valve connection piece 14 of the forward flow pipe 13, a valveunit 25 for controlling the valve opening 16 is arranged so that it canbe displaced against the resistance of a spring 28 supported against aninsert 27 arranged in a screwed-in manner in a filler neck 26 of thereserve chamber 17. The valve unit 25 itself is used for the systempressure control of the cooling system 1 as a relief valve 29 openinginto the atmospherically vented coolant reserve chamber 17.

The valve unit 25 also comprises a venting and return flow valve 30which, as a thermostatic valve of the above-described design, controls,as a function of the temperature, a venting and return flow bore 31,which acts between the reserve chamber 17 and the forward flow pipe 13,in the relief valve 29 constructed as a seat valve.

A closing device 32 of the filler neck 26 of the reserve chamber 17comprises, in addition to the pot-shaped insert 27 which can be screwedin, a closing lid 33, which can be screwed to this insert 27 and has aventing bore 34. In addition, in the bottom 35, which serves as a stopof the spring 28 of the valve unit 25, of a control opening 36 used forchecking the warm charge level in the reserve chamber 17 as well as inthe circumferential part 37, the pot-shaped insert 27 also has ventingducts 38 arranged close to the closing lid.

By means of the above-described arrangement according to the invention,when the closing lid 33, the insert 27 and the valve unit 25 are movedaway from the valve connection piece 14, by way of this valve connectionpiece, cold charging of the cooling system 1 of the internal-combustionengine 2 can take place in rapid sequence. When cold charging asillustrated in FIG. 3 occurs, in comparison to conventional systems, animprovement of functions takes place. Such an improvement occurs becausethe coolant simultaneously reaches the internal-combustion engine 2 andthe radiator 4, and the air situated in the internal-combustion enginecooling jacket can escape during the charging operation by way of theopen reserve chamber 17, on the one hand, and through the opened valve24, on the other hand. Rapid and complete charging which, as is known,can be achieved only by a vacuum, is possible by the illustrated systemwithout additional expenditures.

FIG. 4 illustrates the arrangement 11 in the operation of theinternal-combustion engine 2, in which case the valves 24 and 30 shouldbe closed. Corresponding to the temperature-caused coolant volumeincrease, a clear hysteresis-free connection exists here between thecoolant temperature and the spring force of the pressure spring 20 orthe pressure in the compensation chamber 19.

In addition, the arrangement in the device 11 advantageously provideswarm charging of the cooling system 1 according to FIG. 5 without anylosses of the system pressure and without the risk of a coolantejection. When the valve unit 25 with the effectively closedthermostatic valve 30 is inserted and elastically supported against thescrewed-in insert 27, only the closing lid 33 to the atmosphericallyacted-upon reserve chamber 17 must be removed for a possible rechargingof coolant by way of the control opening 36 in the bottom 35 of theinsert 27. In this case, the system pressure is maintained, in whichcase the absent coolant can be recharged. After the opening of the twoventing and return flow valves 24 and 30 in the course of the nextcooling operation in the internal-combustion engine 2 and the radiator4, trapped air can escape, as illustrated in FIG. 6.

Finally, FIG. 6 shows a special gas removal operation during a coolingoperation of the cooling system 1 after the internal-combustion engine 2is switched off. In this case, air and fuel gas, by way of the openedvalves 24 and 30 and by way of the pressureless reserve chamber 17,escape through the venting ducts 38 and the venting bore 34 in theclosing lid 33 into the atmosphere. Subsequently, coolant advances fromthe reserve chamber 17 into the cooling system 1.

In summary, the charging, venting and pressure control arrangement 11according to the invention has the following advantages.

Pressure in the area of the inlet of the forward flow device 3 into theradiator 4 is limited, in which case emerging coolant is not lost but isstored in the reserve chamber 17 and is supplied to the cooling system 1again during the next cooling operation.

Air/gas and coolant are separated during the pressure buildup phasewhile warming-up.

System venting is performed after each cooling operation; thissuppresses the pump-up tendency of the cooling system 1 caused,particularly in the case of diesel engines, by the fuel gas transferinto the coolant.

The pressure buildup - apart from system-caused quantities, such as theoverall coolant content, the water/glycol mixing ratio and hoseelasticity--depends on and is influenced by one quantity exclusively,specifically, the stiffness of the pressure spring 20.

I claim:
 1. Cooling system for a liquid-cooled internal-combustionengine, comprising:a pump which circulates a coolant, and a charging,venting and pressure control arrangement for controlling system pressurein a forward flow pipe, said arrangement including:a tank in which theforward flow pipe is arranged in a penetrating manner and having a valveconnection piece on said forward flow pipe substantially aligned with afiller neck, a valve unit controlling opposite flow directions receivedin said valve connection piece, a closing device of the filler neckagainst which the valve unit is elastically supported displaceably inthe valve connection piece, the valve connection piece being arranged topenetrate a partition of the tank with a valve opening which opens intoa coolant reserve chamber for a coolant reserve which is acted upon byatmosphere, an elastically flexible device which compensates thermallycaused volume changes to the coolant circulated by said pump, saidelastically flexible device including an additional, geodetically deepercompensation chamber of the tank, having a boundary which can bedisplaced against an elastic resistance, used for coolant volumecompensation, a connection piece connecting the compensation chamberwith a pump suction pipe of the cooling system, and atemperature-controlled venting and return flow valve by which thecompensation chamber is connected with said coolant reserve chamber. 2.Cooling system according to claim 1,wherein the valve connection pieceon the forward flow pipe is constructed so that said valve unit isremovable for cold charging of the cooling system, and wherein, duringwarm charging of the cooling system, said valve unit is inserted andelastically supported in the valve connection piece against a bottom ofan insert detachably arranged in the filler neck, said bottom beingprovided at a warm charging level in the coolant reserve chamber. 3.Cooling system according to claim 2,wherein the closing device of thefiller neck comprises a pot-shaped insert which can be screwed to thefiller neck, and a closing lid which interacts with the pot-shapedinsert and has a venting bore, and wherein the bottom is used as thestop of a spring of the valve unit and the insert has a control openingused for checking a warm charging level as well as venting ductsarranged in a circumferential part close to the closing lid.
 4. Coolingsystem according to claim 3, wherein said boundary of the compensationchamber comprises a displacement piston which is arranged in acoolant-tight manner by roller bellows, andwherein said displacementpiston is acted upon by a pressure spring which is arranged in aprestressed manner supported against the tank.
 5. Cooling systemaccording to claim 3, wherein the charging, venting and pressure controlarrangement with the coolant reserve which is acted upon by atmospherein said coolant reserve chamber is arranged directly in a forward flowfrom the internal-combustion engine to a radiator.
 6. Cooling systemaccording to claim 2,wherein the valve unit comprises a venting andreturn flow valve which is constructionally combined with a reliefvalve, and wherein the venting and return flow valve is designed as athermostatic valve controlling, as a function of the temperature, aventing and return flow bore effective between the coolant reservechamber and the forward flow pipe, in the relief valve designed as aseat valve.
 7. Cooling system according to claim 2, wherein saidboundary of the compensation chamber comprises a displacement pistonwhich is arranged in a coolant-tight manner by roller bellows,andwherein said displacement piston is acted upon by a pressure springwhich is arranged in a prestressed manner supported against the tank. 8.Cooling system according to claim 2, wherein the charging, venting andpressure control arrangement with the coolant reserve which is actedupon by atmosphere in said coolant reserve chamber is arranged directlyin a forward flow from the internal-combustion engine to a radiator. 9.Cooling system according to claim 1,wherein the valve unit comprises aventing and return flow valve which is constructionally combined with arelief valve, and wherein the venting and return flow valve is designedas a thermostatic valve controlling, as a function of the temperature, aventing and return flow bore effective between the coolant reservechamber and the forward flow pipe, in the relief valve designed as aseat valve.
 10. Cooling system according to claim 9,wherein the closingdevice of the filler neck comprises a pot-shaped insert which can bescrewed to the filler neck, and a closing lid which interacts with thepot-shaped insert and has a venting bore, and wherein the bottom is usedas the stop of a spring of the valve unit and the insert has a controlopening used for checking a warm charging level as well as venting ductsarranged in a circumferential part close to the closing lid.
 11. Coolingsystem according to claim 9, wherein said boundary of the compensationchamber comprises a displacement piston which is arranged in acoolant-tight manner by roller bellows, andwherein said displacementpiston is acted upon by a pressure spring which is arranged in aprestressed manner supported against the tank.
 12. Cooling systemaccording to claim 9, wherein the charging, venting and pressure controlarrangement with the coolant reserve which is acted upon by atmospherein said coolant reserve chamber is arranged directly in a forward flowfrom the internal-combustion engine to a radiator.
 13. Cooling systemaccording to claim 1, wherein said boundary of the compensation chambercomprises a displacement piston which is arranged in a coolant-tightmanner by roller bellows, andwherein said displacement piston is actedupon by a pressure spring which is arranged in a prestressed mannersupported against the tank.
 14. Cooling system according to claim 13,wherein the charging, venting and pressure control arrangement with thecoolant reserve which is acted upon by atmosphere in said coolantreserve chamber is arranged directly in a forward flow from theinternal-combustion engine to a radiator.
 15. Cooling system accordingto claim 1, wherein the charging, venting and pressure controlarrangement with the coolant reserve which is acted upon by atmospherein said coolant reserve chamber is arranged directly in a forward flowfrom the internal-combustion engine to a radiator.
 16. Cooling systemfor a liquid-cooled internal-combustion engine, comprising:a pump whichcirculates a coolant, a tank into which a forward flow pipe opens andhaving a valve connection piece on said forward flow pipe substantiallyaligned with a filler neck, a valve unit controlling opposite flowdirections in the tank between a coolant reserve chamber for a coolantreserve which is acted upon by atmosphere and a compensation chamber, aclosing device of the filler neck against which the valve unit iselastically and displaceably supported in the valve connection piece, anelastically flexible device which compensates for thermally causedvolume changes to the coolant and including a displaceable boundarydefining said compensation chamber and which can be displaced against anelastic resistance to compensate for said volume changes, a connectionpiece connecting the compensation chamber with a pump suction pipe ofthe cooling system, and a temperature-controlled venting and return flowvalve by which the compensation chamber is connected with said coolantreserve chamber.
 17. Cooling system according to claim 16, wherein thevalve unit is removable for cold charging of the cooling system. 18.Cooling system according to claim 17, wherein the valve unit comprises aventing and return flow valve which is constructionally combined with arelief valve.
 19. Cooling system according to claim 18, wherein theventing and return flow valve is designed as a thermostatic valvecontrolling, as a function of the temperature, communication between thecoolant reserve chamber and the forward flow pipe.
 20. Cooling systemaccording to claim 16, wherein said displaceable boundary comprises adisplacement piston which is arranged in a coolant-tight manner byroller bellows.
 21. Cooling system according to claim 20, wherein saiddisplacement piston is acted upon by a pressure spring which is arrangedin a prestressed manner supported against the tank.